Safety footwear is often required on construction sites. A primary function of safety footwear, such as safety boots or shoes, is to protect the foot against impacts. Accordingly, some items of footwear include a toe-cap (e.g., steel toe or composite toe). The toe-cap defines a volume accommodating the toes of the wearer in the item of footwear so as to protect the toes against the impact from objects falling against the footwear. In most safety footwear, the toe-cap is within the upper and is therefore under the leather or synthetic material forming the exposed surface of the upper. As the material of the upper is above that of the toe-caps, the material of the upper often rips or is damaged over time as a result of abrasion and impact, thereby exposing the toe-cap material. As they are even used as “hammers” to kick objects, safety boots with toe-caps often wear out prematurely in the toe region.
The premature wearing-out of the leather in the toe region, accentuated by the presence of toe-caps, resulted in shoe manufacturers adding a protective shell over the leather in the toe region. Such a protective shell, commonly referred to as bumper toe, is made of a resistant compound (e.g., polyurethane). By protecting the material of the upper where the upper would normally break and tear, protective shells enhance the durability of the item of footwear.
Some bumper toes are cemented to the uppers prior to the soling process and a portion of such bumper toes is folded and secured under the edge of the last. Some bumper toes are molded during the injection of a midsole in a direct-attach construction. None of these constructions have an extension below the edge of the last.
Therefore, there remains a weakness at the junction between the upper and sole as well as between the midsole and outsole, in the front-end region of the item of footwear. The front-end region is subject to abrasion and/or intense shocks. The weakness is particularly notable in footwear with a direct-attach construction, as this type of assembly accentuates the separation of the different parts of sole and of the sole from upper. Moreover, the use of a low density midsole and the addition of a puncture resistant plate (e.g., steel plate) may emphasize this problem.
Referring to FIG. 1 of the prior art, a pair of safety boots in accordance with the prior art is illustrated. Namely, a regular safety boot is illustrated at 1 whereas a safety boot with protective shell is illustrated at 2. In the safety boots 1 and 2, the upper is illustrated at 3. On the safety boot 1, a toe-cap 4 is exposed through a rupture in leather. The safety boot 2 is similar in construction to the safety boot 1, but features a protective shell 4′, i.e., bumper toe. The bumper toe 4′, typically made of a sturdy material such as high-density plastic, is positioned on the outer surface of the upper 3 in order to protect the material of the upper from abrasion and shocks.
The boots 1 and 2 include a midsole 5, an outsole 6, with a joint 7 between the midsole 5 and the outsole 6. The joint 7 is typically trimmed so as to provide a smooth surface finish for the combination of the midsole 5 and the outsole 6.
There is illustrated by reference numeral 8 in FIG. 1 of the prior art the junction between the upper 3 and the midsole 5. It is a common construction for boots to glue the upper 3 to the midsole 5, or to bond both the upper 3 and outsole 6 in a direct-attach process where the midsole 5 is injected. Accordingly, some prior art construction footwear has been known to split between the upper 3 and the midsole 5, and/or between midsole 5 and outsole 6, at the front-end of the boot. Low density (0.4 to 0.6 kg/m3) injected midsoles are known to tear off quickly as a result of abrasion and impact on the front region of the sole. On the safety boot 2, it is seen that the separation of midsole 5 and outsole 6 creates an opening at 9. Moreover, the puncture resistant plate is seen at 9′. This is a very common problem, called delamination, that occurs even though the safety boot is made with a pre-assembled bumper toe (e.g., cemented bumper toe) or a shell molded during the direct-attach process.